Thanks, Peter.
The trick, if you use a CSS style for numbered lists - and this may be where everyone is getting hung up, is that you have to use RoboHelp's generic list function/button (at the top of the application) to create the list FIRST, and THEN apply your list style from your CSS.
If you create numbered lists by simply applying a list style from your CSS (that is, you never use the RoboHelp application's numbered list button), then you'll never see the restart numbering element.
Finally, to answer my initial question, here's the HTML for restart numbering (where "task" is the name of my CSS numbered list style):
<p> </p>
<ol class="task">
<li>
<p>This step will be auto-formatted as step 1 in the WYSIWYG view/output.</p>
</li>
<li>
<p>This step will be auto-formatted as step 2 in the WYSIWYG view/output.</p>
</li>
<li>
<p>This step will be auto-formatted as step 3 in the WYSIWYG view/output.</p>
</li>
<ol class="task">
<li style="counter-reset: item1 23;" value="24">This step will be formatted/displayed as step 24 in the WYSIWYG view.</li>
</ol>
<p> </p>
This is what the WYSIWYG view/output will look like:
1. This step will be auto-formatted as step 1 in the WYSIWYG view/output.
2. This step will be auto-formatted as step 2 in the WYSIWYG view/output.
3. This step will be auto-formatted as step 3 in the WYSIWYG view/output.
24. This step will be formatted/displayed as step 24 in the WYSIWYG view/output.
Parsing the reset code:
- "counter-reset: item1 23;" is the number/value immediately preceding (23 in this example) the number/value you want displayed (24 in this example - see below).
- value="24" is the number/value you want displayed for the step.
Important: BOTH values must be specified correctly, or your step won't be numbered properly in the WYSIWYG view or output.